There is a clamp for installing a filler pipe or other tubular body on a vehicle body panel or other support member having a locking hole formed thereon, having a first portion being installed on the support member and a second portion being provided rotatably on the first portion, and being configured to hold the tubular body between the first portion and the second portion (for example, Patent Document 1). In Patent Document 1, the first portion has a grommet part for opening and coupling in the locking hole when a screw is fixed inside. The second portion has a through-hole on a portion corresponding to the grommet part in a state in which the tubular body is held between with the first portion. The screw is inserted into the grommet part through the through-hole in the state in which the tubular body is held between the second portion and the first portion. By such configuration, holding of the tubular body using the clamp and coupling of the clamp to the support member are accomplished simultaneously when the screw is inserted into the grommet part through the through-hole.